1. Field of the Invention
The present invention relates to purifying apparatus for purifying outside air supplied to facilities with semiconductor equipment installed, and particularly to purifying apparatus applied to removing aerial chemical contaminants such as particulate contaminants or airborne molecular contaminants included in outside air.
2. Description of Related Art
FIG. 1 is an overall view of an air conditioning unit incorporating an eliminating device for eliminating gaseous molecule impurities including aerial chemical contaminants, and particularly small amounts of water soluble gaseous substance impurities. This system is for use as purifying apparatus for purifying exhaust gas from special facilities or cleaning outside air supplied to a clean room.
In FIG. 1, arranged from the top in order, are a pre-filter 1, a medium efficiency filter 2, a heating coil 3, a cooling coil 4, a gaseous molecule impurity remover 5, a fan 8, a heating coil 9, and a humidifier 10. The gaseous molecule impurity remover 5 consists of a nozzle 6, which injects toward an upstream side supplied with pure water from an external pure water manufacturing plant 13 through a purified water tank 11 using a pump 12, and a group of plates 7 having an eliminator structure arranged at a location separated from the nozzle 6.
The gaseous molecule impurity removing principle of this method is a vapor-liquid contact method which removes gaseous molecule impurities by increasing the efficiency of vapor-liquid contact using a water droplet jet from the nozzle 6 and a hydrophilic eliminator. In this way, by supplying liquid into a packing material having high fluid injection and porosity, in other words a large surface area, the vapor-liquid contact system removes gaseous molecule impurities in air with a removal efficiency equal to that of a dry process using chemical filter, pressure adjustment is easy, it is maintenance free and running costs can also be reduced.
However, the removal method of the related art has the following problems. (a) With a jet method using a nozzle, the vapor-liquid contact efficiency declines due to the effects of the flow efficiency of air flowing inside the apparatus on a jet stream. (b) Since the whole surface of hydrophilic eliminator is usually in a wet state, the flow resistance of the eliminator itself increases and it causes a large pressure loss. (c) The wet state of the eliminator surface also makes it impossible to prevent absorbed water drops from scattering to the downstream side because of the wet state. (d) Since a hydrophilic eliminator is formed in a plate configuration combined with an enhanced chemical material, water drops penetrate the hydrophilic eliminator when water soluble gaseous molecule impurities are removed, lowering the removal efficiency. (e) When dissolving of gaseous molecule impurities into water drops reaches a critical state, it causes gaseous molecule impurities to be re-released into the air resulting in a reduction in the maintenance cycle of the eliminator. (f) Directly supplying pure water into an eliminator and removing gaseous molecule impurities results in a lowering of the moisture removal capability of the eliminator itself and thus its capability for preventing water drop particles scattering to the downstream side. (g) With only an eliminator, since the nozzle is made unnecessary and water is supplied directly, it becomes impossible to control lowering of the vapor-liquid contact efficiency and temperature necessary for air conditioning. (h) Because of scattering of water drop particles from the eliminator, fin component parts of a fan at a downstream side are corroded.
The present invention provides a gaseous molecule impurity removing apparatus for an apparatus for purifying airborne molecular contaminants, having a nozzle section consisted of a group of jet nozzles, with a forward jet nozzle arranged so as to face upstream and a rearward nozzle arranged so as to face downstream. It is also possible for the forward nozzle to face downstream and for the rearward nozzle to face upstream. In an eliminator having a three stage structure, a windmill type fan is built into a central eliminator stage.
As a result a vapor-liquid contact efficiency for the gaseous molecule impurities is increased and a gaseous molecule impurity removal efficiency is improved. Also, it is possible to reduce the space occupied and it is possible to reduce running costs still further.